fails:Regexp.linear_time? returns true for positive lookarounds
fails:Regexp.linear_time? returns true for positive lookahead
fails:Regexp.linear_time? returns true for positive lookbehind
fails:Regexp.linear_time? returns true for negative lookbehind
fails:Regexp.linear_time? returns true for non-recursive subexpression call
fails:Regexp.linear_time? returns true for positive lookahead with capture group
